This invention relates to a tubular gas generator, in particular a tubular gas generator for an inflatable impact cushion such as an air bag of a motor vehicle.
A (tubular) gas generator is disclosed in U.S. Pat. No. 4,005,876, which has an outer tube, in a wall (jacket) of which there are arranged gas outlet openings and the ends of which are closed. In the outer tube there is located an inner tube, also provided in its jacket with gas outlet openings, the outer diameter of the inner tube which is smaller than the inner diameter of the outer tube, so that between the two eccentric tubes there forms an intermediate chamber for receiving a filter and cooling wire mesh. The inner tube, the axial length of which is less than that of the outer tube, is filled with (pressure-)gas-producing material (also called pressure gas-generating charge, for example in the form of pellets), which is ignited by an ignition unit. The gas forming when igniting the gas-producing material passes via the gas outlet openings of the inner tube through the filter material, in order to arrive outside, via the gas outlet openings, in the outer tube. The gas generator is, in the case of use for an impact protection gas cushion, arranged in a housing open at one side, with this opening being closed by a folded fabric, the actual inflatable gas cushion.
Arranged on one axial end of the two tubes there is a closure cover connecting the tubes to each other, which is surrounded by the outer tube in its end section. In the peripheral surface of the closure cover there is formed a peripheral groove, in the region of which the outer tube is pinched-in. The inner side of the closure cover is provided with a recess, into which the axial end of the inner tube is inserted. With the ignition of the gas-producing charge, relatively high pressure occurs in the inner tube and in the intermediate chamber between the two tubes. The closure cover, anchored, as described above, to the outer tube, must be able to resist this high pressure. Because of the circular arc-shaped formation of the peripheral groove and the peripheral interior projection arising out of the contraction there is the danger that closure cover, possibly tilting under the action of the pressure, is loosened from the outer tube. This can lead to damage of the units arranged around the gas generator. The gas emerging via the loosened closure cover is not cleaned and therefore carries along residue from combustion, which can also cause damage. Finally a loosening of the closure cover acts negatively on the burning process and the gas development.